Pigment dispersions, block polymers and manufacturing method therefor

Abstract

Disclosed is a pigment dispersion containing at least a pigment, a liquid medium and a high-molecular dispersant. The high-molecular dispersant is a block polymer represented by A-B or A-B-C, in which A, B and C each represent a polymer block and the A and C blocks may be the same or different. The block polymer and its production process are also disclosed. The high-molecular dispersant is free of problems of a smell, coloration, a heavy metal and cost, and its use can provide a pigment dispersion excellent in the dispersion stability of a pigment.

Description

TECHNICAL FIELD[0001]This invention relates to a block polymer which can be obtained by a novel polymerization process and is controlled in structure. The novel polymerization process is easy to polymerize monomers, assures a good polymerization yield, uses materials which are economical and do not place much load on the environment, and requires no special compound or compounds. The present invention is also concerned with a pigment dispersion containing the block polymer as a high-molecular dispersant and also with its use.BACKGROUND ART[0002]Acrylic copolymers, a kind of polymers formed from ethylenically-unsaturated monomers (which may hereinafter be called simply “monomers”), are used in a variety of fields such as high-molecular dispersants, paints, binders, and self-adhesives. Many of these acrylic copolymers are produced by general radical polymerization. According to such general radical polymerization, however, a termination reaction such as the recombination of propagatin...

AI Technical Summary

Benefits of technology

[0030]The process for obtaining the block polymer (high-molecular dispersant) in the present invention does not use any heavy metal, does not absolutely need the purification of the polymer, does not require the synthesis of special compounds, and can readily obtain the target product from only relatively economical materials available on the market. Further, the polymerization conditions are mild, and the polymerization can be conducted under similar conditions as the conventional radical polymerization processes, does not require any special equipment, can use conventional radical polymerization equipment, and is not affected much by water or light. Further, the monomers, solvent and the like to be used do not require purification, and monomers having various functional groups can be used to introduce them into the polymer. In addition, the polymerization degree is very high.

[0031]The block polymer useful as a high-molecular dispersant in the present invention is significantly characterized in that its polymerization is initiated from the initiating compound. By adding and polymerizing the monomer b after the polymerization and formation of the polymer block A from the monomer a, the A-D block polymer having the polymer block D, which contains glycidyl groups or isocyanate groups, can be obtained. By further polymerizing the monomer a to form the C block, the A-D-C triblock polymer can be obtained.

[0032]By further adding and reacting the compound E, which has an amino group or hydroxyl group, to the resultant polymer block D having glycidyl groups or isocyanate groups, an addition reaction readily takes place with the glycidyl groups or isocyanate groups. By this method, block polymers having various functional groups can be obtained. Further, depending on the structure of the compound E to be added, block polymers can be obtained with various physical properties, thereby making it possible to provide them as high-molecular dispersants having structures suited for the dispersion of various pigments.MODES FOR CARRYING OUT THE INVENTION

[0033]The present invention will hereinafter be described in further detail based on preferred embodiments.

[0034]The polymerization process for use in the present invention is novel living radical polymerization. Different from the conventional processes, this living radical polymerization uses neither a metal compound nor a ligand, and further, does not use any special compound such as a nitroxide compound, dithiocarboxylate ester or xanthate compound. This living radical polymerization can be readily conducted by simply using an initiating compound and a catalyst in combination in the conventional radical polymerization.

[0035]The above-described polymerization process proceeds through a reaction mechanism represented by the following reaction formula (1), and is a reversible activation reaction of a dormant species, Polymer-X (P-X), into a propagating radical.Although this polymerization mechanism may vary depending on the kind of a catalyst, the polymerization mechanism is considered to proceed as will be described next. In the reaction formula (1), P• generated from the radical initiator reacts to XA to form a catalyst A• in situ. A• acts as an activator for P-X, and owing to its catalytic effect, P-X is activated at high frequency.

Problems solved by technology

However, the above-described living radical polymerization processes are accompanied by such problems as will be described next.

Moreover, with this polymerization process, polymerization of a methacrylate monomer is not allowed to proceed in general.

Even with this method, there is a potential problem that the polymerization may terminate halfway.

With this process, it is, therefore, difficult to polymerize an addition-polymerizable monomer containing an acid group.

It is hence not easy to introduce acid groups into the resulting polymer block.

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